RF Attenuator design

[cjrathi]

Hi ,

I want to design 90 dB digital attenuator using attenuator parts (IC). Please suugest some related documents related to RF PCB design of attenuator, inclusion of any other ICs for proper operation, selection of matching networks, etc


Thanks
Chaitanya

 

[BabaYaga]

Hi Chaitanya,
If you are new to the RF design, then refer to the below document which briefs about the important points that you need to consider while designing with attenuators.

https://www.minicircuits.com/app/ATT4-2.pdf

And if you are looking out for any parts and some more theory on Digital step attenuators then refer the below document link.

https://www.minicircuits.com/app/AN70-004.pdf

As far as RF PCB Design is concerned first finalize what will be your schematic or design then you can think about the pcb design, it wouldn't be that complex only you need to follow some guidelines.

Let me know once you start you RF Pcb Design i would be happy to help.

Thank You

 

[cjrathi]

Thanks Bhavani for getting back so early..

I am pretty much aware of RF circuit and PCB design concept.

Actually I am trying to modify one existing 90 dB digital attenuator design. Its drawback is that it becomes nonlinear after i give attenuation level of 70 dB.

What modification that can be done in the schematic?

Thanks

 

[BabaYaga]

What dielectric material are you using in your PCB, i'm guessing it to be FR-4?

 

[cjrathi]

Yes.. it is FR4 substrate...

- - - Updated - - -

Yes.. it is FR4 substrate... and it will be 4 layer PCB board..

 

[Element_115]

Yes.. it is FR4 substrate...

- - - Updated - - -

Yes.. it is FR4 substrate... and it will be 4 layer PCB board..

Depending on the geometry of your Attenuator you may not be able to get
90dB.
One company that has good Isolation is call Peregrine. They use Sapphire to
achieve good isolation. They may have good info on this topic.

On a PCB you may have leakage due to parasitic of your board and/or layout
(traces). What Frequency are you designing to ? You may have to make two
45dB Attenuators and keep them as far apart as possible to get 90dB. Also
during testing you will want to use a powerful signal so you can measure it's
attenuation and not be limited by the receivers (Spectrum Analyzer?)
noise floor. You will also have to take much care with good grounding.

Good luck.

 

[FvM]

Information is really sparsely in your questions. Frequency range? IC type?